The present invention is particularly adapted for use with vehicles which travel over a roadway or guideway having longitudinal side guides which are engaged by guideaxles and wheels at the front and rear of the vehicle for sensing a curvature in the side guides and for causing turning of both the front and rear wheels of the vehicle to negotiate a turn in the roadway. Turning of both the front and rear wheels is desired to cause the vehicle to accurately follow a small radius curve without lateral slippage of pneumatic tires or the like on the vehicle and without bumping against the side guides as would occur, for example, if only one set of wheels were steerable.
On guided vehicles of this type with independent front and rear steering, the steering sense (i.e., the direction of wheel rotation which results from a guideaxle displacement in one direction) is opposite for front and rear steering. For example, in a left turn the front guideaxle may bear on the right-hand side guide and is displaced to the left causing a counterclockwise rotation of the front wheels about their kingpins when viewed from above. On the other hand, the rear guideaxle bears on the left-hand side guide and is displaced to the right to cause clockwise rotation of the rear wheels. When the vehicle direction of motion is reversed, the steering sense of the front and rear steering mechanisms must be reversed also. A reversing mechanism for this purpose must provide reversed steering sense upon application of an actuator force and hold position without continuous application of the force. At the same time, it should be compact, provide for minimum lost motion, and preferably be enclosed for all-weather operation.
In the past, various systems for reversing the steering sense of guided vehicles have been provided including one which manually translates a control arm attachment across the steering arm fulcrum. This arrangement, however, is manual, must be performed in a maintenance facility, necessitates moving the control rod through a large space envelope and is vulnerable to contamination or icing. Another method previously used reverses steering sense by alternating the links that couple the guideaxle to a reversing toggle. Here, again, the coupling links require a large space envelope and protection during all-weather operation is not readily possible.